docs: i2c: i2c-protocol: fix kernel-doc function syntax

This clarifies these are functions and adds a hyperlink to the function
documentation.

Signed-off-by: Luca Ceresoli <luca@lucaceresoli.net>
Reviewed-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

Documentation/i2c/i2c-protocol.rst

@@ -28,7 +28,7 @@ Count (8 bits): A data byte containing the length of a block operation.
 Simple send transaction
 =======================
 
-This corresponds to i2c_master_send::
+This corresponds to i2c_master_send()::
 
   S Addr Wr [A] Data [A] Data [A] ... [A] Data [A] P
 
@@ -36,7 +36,7 @@ This corresponds to i2c_master_send::
 Simple receive transaction
 ==========================
 
-This corresponds to i2c_master_recv::
+This corresponds to i2c_master_recv()::
 
   S Addr Rd [A] [Data] A [Data] A ... A [Data] NA P
 
@@ -44,7 +44,7 @@ This corresponds to i2c_master_recv::
 Combined transactions
 =====================
 
-This corresponds to i2c_transfer
+This corresponds to i2c_transfer().
 
 They are just like the above transactions, but instead of a stop bit P
 a start bit S is sent and the transaction continues. An example of